Analog film/screen projection radiography supports conventional film sizes (e.g., 18×24 cm., 24×30 cm., 35×35 cm., and 35×43 cm.) that are selected based upon the size of the object (bodypart) being imaged. Digital systems such as computed radiography (CR) and direct radiography (DR), are replacing analog film radiography systems for various reasons—for example, improved image quality and network distribution of information. CR utilizes storage phosphor cassettes, which are a direct replacement of analog film cassettes, thus, cassette sizes are the same and selection of the plate is dictated by the bodypart being examined. If a small anatomical structure is being imaged, e.g., a finger, the smallest (e.g., 18×24 cm.) plate is typically used. When the CR image is read out and sent to a workstation for interpretation, it will be properly displayed on a high resolution display without appreciable further manipulation by the end-user (radiologist, diagnostician). This is typically because the sizes of the cassettes and the resolution of the image capture are consistent with the image area and pixel resolution available on the display.
A common practice in CR that is carried over from analog film practices is using a larger cassette to capture multiple views of a bodypart on a single cassette. When this is done, typically the image containing multiple views is displayed to fill the full screen (referred to as “fit-to-screen”) causing the anatomy to be smaller than true size. The end-user is forced to pan and zoom the image prior to interpretation which is inefficient and undesirable.
Direct (and indirect) radiography (DR) is an alternate newer technology for obtaining digital projection radiographs. DR utilizes a flat-panel imager which incorporates a thin film transistor (TFT) array to convert incident x-rays to discrete pixels via photodiodes (indirect conversion) or storage capacitors (direct conversion). The DR flat-panels are large area fixed size devices, typically 35×43 cm. or 43×43 cm. with the resulting image having a corresponding large image area. Thus, as mentioned above, a small anatomical structure acquired on a large area DR panel typically results in wasted time by the end-user in panning and zooming the image when the image is displayed on a workstation in a “fit-to-screen” mode.
Display of projection radiographs is typically managed by a picture archiving and communication system (PACS) and industry standards exist which facilitate interoperability between vendors. The standards are defined by the Digital Imaging and Communications in Medicine (DICOM) organization and subcommittees. DICOM has made provisions for display protocols to facilitate appropriate soft-copy presentation of an image for diagnostic interpretation. For example, DR modalities which utilize the direct x-ray information object definition (DX IOD) can specify “field of view” information as part of the DX detector module attributes. Utilization of this aspect of DICOM can facilitate good management of images for display in PACS. But some aspects of the standards are optional, and not all PACS vendors implement the optional features. Thus, in some situations, dependent upon the acquisition modality (e.g., CR or DR IOD tags) and PACS vendor's DICOM implementation and capabilities, inefficient of the radiologist's time may be required. Therefore, it becomes the responsibility of the modality (CR or DR) to most efficiently manage the information being sent to the PACS—either by supplying information about the exposure field in the form of DICOM information, or by cropping extraneous information to efficiently utilize bandwidth, both from the perspective of digital data transmission, and data storage in the archive.
There is a need for an imaging process which solves this problem, namely, that large area projection radiographic images (DR or larger cassette CR) are more efficiently handled (displayed, transmitted, and stored) when exams of smaller anatomical structures are acquired.
U.S. Pat. No. 6,654,506, issued Nov. 25, 2003, inventors Luo et al., discloses a method for automatically creating cropped and zoomed versions of photographic images. The method uses a probalistic approach to automatically determine a crop window. A belief map is required a prior in which a belief value at a particular pixel location indicates an importance of a photographic subject at the same location in the photographic image. The belief map drives the placement of the crop window, the size of which is set by the user in advance as an input to the system. The user specifies the crop size (i.e., the crop window) and a magnification factor as input to the processing. This process, although useful for the purpose for which it was intended, may be disadvantageous in using subject probability and in requiring these latter inputs.
U.S. Pat. No. 6,091,841, issued Jul. 18, 2000, inventors Rogers et al., discloses a method and system for segmenting desired regions in digital mammograms. The method is related to automatic microcalcification detection and classification and discloses an automated segmentation method which utilizes iterative morphological operations in combination with signal normalization (via histogram equalization) and region growing to define a binary mask of a breast image. The crop window is then defined as the rectangular boundary that encompasses the binary mask. There is no provision for a rotated exposure field crop window such that a rotated crop window would result, nor is there provision for multiple exposure fields.
U.S. Pat. No. 4,620,098, issued Oct. 28, 1986, inventor Fujiwara, is directed to a radiation photographing apparatus.
U.S. Pat. No. 6,081,267, issued Jun. 27, 2000, inventors Stockham et al. relates to a method for displaying radiological data.
U.S. Pat. No. 6,317,510, issued Nov. 13, 2001, inventor Murakami is directed to a blackening processing method and apparatus.
U.S. Pat. No. 6,704,440, issued Mar. 9, 2004, inventor Kump is directed to a method and apparatus for processing a medical image.